Tuesday, 11 July 2017 05:18

4 strategies for increasing your hardwood forest yield

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By: Al Koeppel, Forester, Kretz Lumber Company

Whether you take a very active land management approach, or are just starting to think about it, there are a number of strategies you can use to increase the yield of your hardwood stand. Here are four tips you should consider as you think about increasing your forest yield.

Volume and Value

When we talk about increasing yield, we need to consider volume and value. Let’s start with volume. Take any tree in a well managed forest and as you chart its growth, it will generally follow a typical bell shaped curve. We call this “mean annual increment” or MAI. Consider a red pine planted as a seedling. During those first few decades, it experiences a lot of growth. At around age 60, it starts slowing up on volume growth. The tree will continue to put growth on as it will typically live to 150+ yrs. old, but the volume growth per year will slow down.

Now, let’s look at this same red pine and take into consideration its value growth. Do you think that its value growth, or what I like to refer to as economic growth, is the same as MAI? That would be a somewhat typical assumption. The lion’s share of the time this is not the case though. As the tree grows in size and increases its merchantable volume, it also increases in grade. 

Grow high quality trees

Seems like a no brainer, but there is a lot that goes into determining the quality of a tree. Trees are sold by product classes. Wood product classes are based on two major factors: defects and diameter. Our red pine example is generally classified as pulpwood, the lowest valued wood. If no defects are visible, then the diameter of the tree will determine what product class the tree falls into. 

  • Product classes for red pine = pulp, bolts, utility poles
  • Product classes for hardwood = pulp, bolts, sawlogs, veneer logs

 

When it comes to product classes, the most important thing to understand is that each different product class has an increase in value. As the tree grows in size, at certain sizes it jumps to the next product class and you are rewarded with a volume increase plus the value increase (pretty cool, isn’t it?).  At some point in the tree’s life, it hits the highest product class and you are then only collecting on the volume growth. I’ve been talking about red pine up until this point of the article. Hardwood is more complicated. The basics are the same, you want to grow your trees at a maximum growth rate along with product class increases and then harvest your trees when your peak rate of return nears the top of the bell shaped curve I mentioned earlier. An experienced forester can assist in determining the best time to plan your harvest.

In hardwood there are multiple grades of sawlogs and multiple grades of veneer logs. You also have to consider color issues for certain species of hardwood.  Along with all the grades, there can be considerable value differences between products. Generally speaking, the bottom half of the tree is where your highest product class is located. A good rule of thumb is to harvest your tree when the bottom half is no longer increasing in grade.

Don’t over crowd or under utilize your land

Up until this point, we’ve just been focused on a single tree. Now let’s look at the whole stand. You want to make sure that every square foot of woodland is being utilized. This can be looked at as what is called the stocking level and is measured in square feet per acre as basal area. Keeping trees growing tightly together will help them prune off their lower branches and create a straight clean bole. However if you keep too many trees per acre, the competition is so fierce that they may become weak and are less resistant to fighting disease and insects. It’s important to keep the stocking level optimized to prevent this. When your basal area gets around 120 to 130 square feet per acre, you should thin the stand down to around 75 to 85 square feet.

By choosing your poorest quality trees to harvest first, you not only increase the overall value of your stand by leaving the best and highest value trees, you also take away competition. On the other end of the spectrum, you need to harvest your good trees when they have gotten to economic maturity. Sounds pretty simple doesn’t it?  The basic concept is straightforward, but the more challenging part is understanding what quality is. There is a learning curve to understanding the subtleties between grades especially in the higher value products. Which brings me to my next point…

Understand log quality, grade and defects

In your forest today, you may have two trees standing side by side that are the same diameter and the same height. You’d think the value would be the same, but that is not always the case. The value can be drastically different. Things such as bird peck, pin knots, and damage to the crown will all affect the value of a tree. 

When selling your logs, buyers will look at three main factors: Grade, scale and species. Grade is a measure of the quality of the log and the lumber that the log will produce. Scale is a measure of the quantity of lumber within the log. And species is fairly straightforward. Certain species of tree provide much more highly valued lumber than others. 

Final thoughts

To sum it up:

  • Balance is key. You need the correct number of trees per acre (basal area).
  • Put your growth on high quality trees.
  • Harvest your trees at the right point in time.
  • Understand quality, grade and defects.

This is always easier to accomplish when working with a knowledgeable professional. All foresters can learn this information but when it comes to understanding quality, industrial foresters work with this on a daily basis. As a landowner, get involved. Don’t be afraid to ask questions. In my experience, the more knowledgeable the landowner, the better the experience. 

Have questions or want assistance in increasing the yield of trees on your property? Contact our forestry services team or call Al at 800-352-1438. We can help you design plans that meet your goals and have the best interest of your forest in mind. 

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